HD64F2621 datasheet(97/1069 Pages) RENESAS

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Section 3 MCU Operating Modes

Rev. 5.00 Jan 10, 2006 page 73 of 1042

REJ09B0275-0500

Section 3 MCU Operating Modes

3.1

Overview

3.1.1

Operating Mode Selection

The H8S/2626 Group and H8S/2623 Group have four operating modes (modes 4 to 7). These

modes enable selection of the CPU operating mode, enabling/disabling of on-chip ROM, and the

initial bus width setting, by setting the mode pins (MD2 to MD0).

Table 3.1 lists the MCU operating modes.

Table 3.1

MCU Operating Mode Selection

External Data Bus

MCU

Operating

Mode

MD2 MD1 MD0

CPU

Operating

Mode

Description

On-Chip

ROM

Initial

Width

Max.

Width

00—

—

1—

Advanced

Disabled

16 bits

On-chip ROM disabled,

expanded mode

8 bits

16 bits

On-chip ROM enabled,

expanded mode

Enabled

8 bits

16 bits

Single-chip mode

—

Note:

Not available in the H8S/2626 Group or H8S/2623 Group.

The CPU’s architecture allows for 4 Gbytes of address space, but the H8S/2626 Group and

H8S/2623 Group actually access a maximum of 16 Mbytes.

Modes 4 to 6 are externally expanded modes that allow access to external memory and peripheral

devices.

The external expansion modes allow switching between 8-bit and 16-bit bus modes. After program

execution starts, an 8-bit or 16-bit address space can be set for each area, depending on the bus

controller setting. If 16-bit access is selected for any one area, 16-bit bus mode is set; if 8-bit

access is selected for all areas, 8-bit bus mode is set.

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